The heavy fermion superconductor OPd2Al3 exhibits the unusual combination of an antiferromagnetic phase transition, at TN= 14.3 K, followed by a superconducting phase transition below 2 K without destruction of the ordered magnetic moment. Polarised inelastic neutron scattering reveals the presence of two coupled modes both transverse to the sub-lattice magnetisation. On passing into the superconducting phase an abrupt change is observed in the magnetic inelastic response. We show that it is reasonable to consider the superconducting state as an arising out of interactions between quasiparticles which are strongly renormalised by the low frequency exchange field.